Chromosomes
T.H. Morgan: first to associated genes with chromosomes
worked with Drosphila melanogaster(fruit flies)
Fruit flies produce 100s of offspring, new generation every 2 weeks, only 3 autosomal and 1 sex chromosome
wild type: the normal/most common phenotype in natural populations
mutant: the opposite of wild type
sex-linked/X-linked: genes located on sex/X chromosome
Y chromosomes has few genes, so most mutants are on the X chromosome
genes on the same chromosome passed along as a unit
genes on the same chromosome are linked
linked genes don’t follow the Law of Independent Assortment
Genetic map: an ordered list of loci along a chromosome
genetic map was constructed by: Sturtevant, Morgan’s student
linkage map: created by associating frequencies of recombinants along the chromosomes
the farther apart the two genes, the high the chance that a crossover will occur, and higher the recombination frequency
1 map unit(mu) = 1% chance of recombination
more than 50 mu indicates no linkage
males determine gender of offspring
For a female to express a recessive sex-linked allele, she must be: homozygous recessive
hemizygous: only one locus(one X to be expressed)
X-linked recessive disorders: re-green color blindness, Duchenne muscular dystrophy, hemophilia
X-inactivation: only one of two X chromosomes are active in each cell
Barr body: the inactive, condensed X chromosome
Where are the Barr body chromosomes reactivated? ovaries
Calico cats are only female, only male when: XXY (Klinefelter’s)
Nondisjunction: gametes having one extra and one less chromosome
Nondisjunction is caused by: error in homolog separation in anaphase I and sister chromatid separation in anaphase II
aneuploidy: abnormal chromosome number
trisomy: three chromosomes in a gamete
monosomy: one chromosome
polyploidy: entire extra set of chromosomes; common in plants
trisomy 21: down syndrome
Klinefelter’s: extra X chromosome
Jacob’s syndrome: extra Y chromosome
trisomy X: shows no difference from the normal XX
Turner’s Syndrome: monosomy X
Cri du chat: deletion in chromosome 5
Leukemia: reciprocal translocation
T.H. Morgan: first to associated genes with chromosomes
worked with Drosphila melanogaster(fruit flies)
Fruit flies produce 100s of offspring, new generation every 2 weeks, only 3 autosomal and 1 sex chromosome
wild type: the normal/most common phenotype in natural populations
mutant: the opposite of wild type
sex-linked/X-linked: genes located on sex/X chromosome
Y chromosomes has few genes, so most mutants are on the X chromosome
genes on the same chromosome passed along as a unit
genes on the same chromosome are linked
linked genes don’t follow the Law of Independent Assortment
Genetic map: an ordered list of loci along a chromosome
genetic map was constructed by: Sturtevant, Morgan’s student
linkage map: created by associating frequencies of recombinants along the chromosomes
the farther apart the two genes, the high the chance that a crossover will occur, and higher the recombination frequency
1 map unit(mu) = 1% chance of recombination
more than 50 mu indicates no linkage
males determine gender of offspring
For a female to express a recessive sex-linked allele, she must be: homozygous recessive
hemizygous: only one locus(one X to be expressed)
X-linked recessive disorders: re-green color blindness, Duchenne muscular dystrophy, hemophilia
X-inactivation: only one of two X chromosomes are active in each cell
Barr body: the inactive, condensed X chromosome
Where are the Barr body chromosomes reactivated? ovaries
Calico cats are only female, only male when: XXY (Klinefelter’s)
Nondisjunction: gametes having one extra and one less chromosome
Nondisjunction is caused by: error in homolog separation in anaphase I and sister chromatid separation in anaphase II
aneuploidy: abnormal chromosome number
trisomy: three chromosomes in a gamete
monosomy: one chromosome
polyploidy: entire extra set of chromosomes; common in plants
trisomy 21: down syndrome
Klinefelter’s: extra X chromosome
Jacob’s syndrome: extra Y chromosome
trisomy X: shows no difference from the normal XX
Turner’s Syndrome: monosomy X
Cri du chat: deletion in chromosome 5
Leukemia: reciprocal translocation
